Cadaveric Dissections Based on Observations of Injuries to the Temporal Bone Structures following Head Trauma

ABSTRACT

One hundred temporal bones obtained from forensic autopsies were dissected to expose injured structures. Longitudinal fractures were present in 82%, transverse fractures in 11%, and mixed fractures in 7% of the cases. Facial canal injuries were present in almost half of the bones with longitudinal fractures (36/82), although cuts of the facial nerve stem were rarely encountered. Damages to the facial canal associated with longitudinal fractures were most frequently seen in the region of the geniculum. However, transverse fractures with facial canal involvement (7/11) most frequently occurred in the labyrinthine portion, causing a complete cut of the facial nerve. Injuries to the jugular bulb were also common (21/100) and associated with all types of temporal bone fractures. Observed damages to the auditory ossicles included disconnection of their joints or fractures of the malleus or stapes. Fractures of the incus were not observed. Injuries to the carotid canal were common (52/100), although an injury to the arterial wall was observed in only one specimen. The frequency and nature of damage in temporal bone fractures strictly reflect the type of fracture, especially in terms of facial nerve disorders: the most serious damage is observed with fractures that involve the otic capsule.

KEYWORDS

Temporal bone - fractures - cadavers - anatomy

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Dr. Wysocki presents a well-done, careful, and systematic microanatomical study on 100 consecutive temporal bone fractures associated with fatal head injury. Autopsy studies with these kind of numbers are becoming increasingly rare, particularly in the United States, yet a tremendous amount of information can come from them. This study is a good example.

He found that 82% of fractures were longitudinal, 11% transverse, and 7% mixed, which is not unexpected. He found a surprising incidence of facial canal disruption (37%) associated with longitudinal fractures, but nerve disruption occurred in only 7% versus 63% of cases of transverse fracture. He also noted a surprising incidence of ossicular disruption, fracture, or both, as well as jugular bulb injury. Both of these latter findings seem significantly higher than clinical experience would suggest and may reflect the severity of temporal bone fractures associated with fatal head injury, as opposed to basilar skull fractures associated with lesser degrees of survivable closed head injury.

The incidence of carotid canal fracture (52%) is very interesting given Dr. Wysocki's finding of carotid artery injury in only 1 case. Clinical experience suggests that angiographic abnormalities will be present in 42% of cases studied for the presence of a basal skull fracture involving the carotid canal,[1] and as many as 18% of patients with carotid canal fractures may develop clinically symptomatic vascular complications.[2] The likely explanation for this discrepancy is that basal skull fractures through the carotid canal probably lead to intimal dissection as the most common injury, subsequently resulting in thrombosis or embolization rather than transmural disruption. I suspect that Dr. Wysocki's autopsy studies are less sensitive to detecting intimal injury as opposed to transmural disruption through the adventitia. From a clinical standpoint, we need to maintain heightened vigilance for vascular sequelae when carotid canal fractures are identified. Whether or not routine further screening (angiography, computed tomography angiography, magnetic resonance angiography) is a cost-effective approach remains the subject of ongoing debate.[1] [3]

REFERENCES

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